Mammography apparatus is used for examining patients' breasts using X-rays. The image is acquired using an image receiver formed either by a photographic plate or by digital sensing means. Examinations practiced with such apparatus comprise taking cranio-caudal and lateral images Cranio-caudal views are obtained by irradiating the breast from above so as to obtain a view in the axis running from the patient's head to her feet. To obtain a side view, the breast is irradiated from the side so as to obtain a view in an axis passing through the patient's body. In both cases, or for views taken in other directions, it is useful for the practitioner when establishing the diagnosis to compare the images of both of the patient's breasts taken in the same direction. Practitioners often put the films of each breast on the negatoscope side by side in order to compare the images of the two breasts. Comparison notably allows structural disorganization within the breast to be located.
A digital mammograph known as the Senographe 2000D is commercially sold by the assignee of the application. Image display protocols are provided for image display. In certain protocols, the images of both breasts in a given direction are displayed side by side. The mammograph also has a “fit to breast” function. This function allows, for a given image, an enlarged view of a region of interest of the breast to be displayed. This region of interest is constituted by the smallest rectangle of the image that contains the complete breast. Margins are nevertheless provided around the breast. One problem encountered with this apparatus is that display does not necessarily allow ready comparisons of the images of both breasts.